Hormone Initiating Ferguson’s Reflex

Ferguson's reflex is initiated by:

Correct Answer: Oxytocin

Ferguson's reflex is a neuroendocrine positive feedback reflex initiated by oxytocin. During parturition (and during nursing), stretching/distension of the cervix and vagina sends afferent nerve impulses to the hypothalamus, causing release of oxytocin from the posterior pituitary, which then causes stronger uterine contractions — this is the Ferguson reflex.

The Ferguson Reflex Mechanism

1. Foetus descends → cervix/vagina stretches
2. Stretch receptors send signals to hypothalamus via spinal cord
3. Hypothalamus triggers release of oxytocin from posterior pituitary
4. Oxytocin stimulates stronger myometrial contractions
5. Stronger contractions push foetus further → more cervical stretch → more oxytocin → positive feedback loop

Clinical Importance

Understanding this reflex explains why oxytocin injections are used to induce/augment labour. Epidural anesthesia can block this reflex by interrupting the afferent nerve signals from the cervix.